Search Talks

After reframing the question of the status of the quantum state in terms of J.S. Bell's "beables", I will sketch out a new theory which -- though nonlocal in the sense required by Bell's theorem -- posits exclusively local beables. This is a theory, in particular, in which the quantum mechanical wave function plays no role whatsoever -- i.e., a theory according to which nothing corresponding to the wave function actually exists. It provides, therefore, a concrete example of how the wave function might be regarded as (at best) "epistemic".

The screening of electric charge in plasma with Bose condensate of a charged scalar field is calculated. In all previous calculations before 2009 the effects of Bose condensation have not been considered. Due to the condensate the time-time component of the photon polarization tensor in addition to the usual terms k-squared and Debye mass squared, contains infrared singular terms inversely proportional to k and k-squared. Such terms lead to power law oscillation behaviour of the screened potential, which is different form Friedel oscillations known for fermions. An analogue of Friedel oscillations in bosonic case is also considered.

All known hidden variable theories that completely reproduce all quantum predictions share the feature that they add some information to the quantum state "psi". That is, if one knew the "state of reality" given by the hidden variable(s) "lambda", then one could infer the quantum state - the hidden variables are additional to the quantum state. However, for the case of a single 2-dimensional quantum system Kochen and Specker gave a model which does not have this feature – the non-orthogonality of two quantum states is manifested as overlapping probability distributions on the hidden variables, and teh model could be termed “psi-epistemic”. A natural question arises whether a similar model is possible for higher dimensional systems. At the time of writing this abstract I have no clue. I will talk about various constraints on such theories (in particular on how they manifest contextuality) and I'll present some examples of failed attempts to construct such models for a 3-dimensional system. I will also discuss a very artificial tweaking of Bell’s original hidden variable model which renders it psi-epistemic for some (though not all) of the corresponding quantum states.

The subject of this conference is the Quantum State --- what the hell it is. A central issue is whether quantum states describe reality (the ontic view) or an agent's knowledge of reality (the epistemic view). Advocates of the epistemic view maintain that many quantum puzzles and conundra are artifacts of an inappropriate reification of strictly epistemic concepts. To provide a broader context for such considerations, I argue that even in classical physics we have got into major trouble by inappropriately conferring physical reality on the abstractions we have used to organize what we know.